• Journal of computational fluids engineering
• /
• v.8 no.2
• /
• pp.1-7
• /
• 2003

The V2F turbulence model, which has shown very good performance in several test cases at low speeds, has been applied to supersonic ramp flow with 20. corner angle at the free stream Mach number of 2.79. The flow is known to manifest strong shock wave/turbulent boundary layer interactions. As a comparative study, low-Reynolds k-ε models are also considered. While the V2F model predicts wall-pressure distribution well, it relatively predicts larger separation bubble and higher skin-friction after the reattachment than the experimental data. Although the ellpticity of f equation is the characteristics of incompressible flows, the converged solutions are acquired in the compressible flow with shock waves. The effect of the realizability constraints used in the model is also examined. In contrast to the result of impinging jet flows, the realizability bounds proposed by Durbin deterioate the overall solutions of the supersonic ramp flow.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.05a
• /
• pp.865-870
• /
• 2001

This paper propose a new seismic detail for ductility enhancement by interlocking spiral reinforcement in the potential yield regions of a wall. Through the theoretical consideration and experiment program, confinement with interlocking spirals lead the structural walls to ductile behavior. All specimens show stable hysteretic behavior and good energy dissipation capacity. Also the increase of shear strength mainly induces a flexural failure mode. As interlocking spiral are used in lapped splice region, they increase the bond strength and prevent a early tensile failure caused by the loss of bond stresses. Consequently, the confinement with interlocking spirals may result in a lower value of force reductions factor, newly proposed detail will be provide more economical design.

• Journal of Electrochemical Science and Technology
• /
• v.10 no.4
• /
• pp.345-360
• /
• 2019

Polymer Electrolyte Membrane Fuel Cells (PEMFC) is one of the leading advanced energy conversion technology for the use in transport. It generates water droplets through the catalytic processes and dispenses the water through the gas-flowed microchannels. The droplets in the dispensing microchannel experience g-forces from different directions during the operation in transport. Therefore, this paper reviews the computational modelling topics of droplet dynamics behaviour specifically for three categories, i.e. (i) the droplet sliding down a surface, (ii) the droplet moving in a gas-flowed microchannel, and (iii) the droplet jumping upon coalescence on superhydrophobic surface; in particular for the parameters like hydrophobicity surfaces, droplet sizes, numerical methods, channel sizes, wall conditions, popular references and boundary conditions.

• Journal of computational fluids engineering
• /
• v.4 no.3
• /
• pp.21-27
• /
• 1999

In this paper, tile characteristics of flow resulting from the configurations of piston head and intake-port of the cylinder in a gasoline-direct-injection engine are investigated numerically. Calculations are carried out from intake process to the end of compression. GTT code which includes the third order upwind Chakravarthy-Osher TVD scheme and κ-ε turbulence model with the law of wall as a boundary condition. As a result, a piston head with a smaller radius of curvature and larger radius gives stronger reverse tumble. It is also shown that as the maximum tumble ratio increases by the configuration of the intake-port the tumble ratio at the end of compression stroke increases. It is concluded that flows at the end of compression stroke can be controlled by the optimum design of intake-port and piston head.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.8
• /
• pp.1088-1094
• /
• 2002

A channel flow with a high Reynolds number but coarse grids is numerically studied to investigate the prediction possibility of its turbulence which is three-dimensional and time-dependent. In the present paper, a Reynolds-Averaged Navier-Stokes (RANS) model, a Large Eddy Simulation (LES) and a Navier-Stokes equation with no model are tested with a new approach of hybrid RANS/LES, which reduces to RANS model in the boundary layers and at separation, and to Smagorinsky-like LES downstream of separation, and then compared with each other. It is found that the simulations of hybrid RANS/LES method sustain turbulence like those of LES and with no model, and the results are stable and fairly accurate. This indicates strongly that gradual improvements could lead to a simple, stable, and accurate approach to predict turbulence phenomena of wall-bounded flow.

• Journal of Energy Engineering
• /
• v.11 no.3
• /
• pp.262-268
• /
• 2002

The present paper investigated the effect of ultrasonic vibrations on the melting process of phase-change materials (PCM). Furthermore, the present study considered constant heat-flux boundary condition, whereas many of the previous researches had adopted constant wall-temperature condition. The results of the present study revealed that ultrasonic vibrations accompanied the effects like acoustic streaming, cavitation, and thermally-oscillating flow. Such effects are a prime mechanism in the overall melting process when ultrasonic vibrations are applied. They speed up the melting process as much as 2.5 times, compared with the result of natural melting. Also, energy can be saved by applying ultrasonic vibrations to the natural melting. In addition, temperature and Nusselt numbers over time provided a conclusive evidence of the important role of ultrasonic vibrations on the melting phenomena.

• Journal of the Korean housing association
• /
• v.14 no.2
• /
• pp.9-18
• /
• 2003

The vitality of a main street is essential to get the urbanity of the urban residential estates. The purpose of this study is to analyze the relationship between the vitality of a main street and street land uses in the residential estate. The outcomes of this study are as follows: first, the street land uses have influence on the vitality of a main street; the main streets with the small commercial and business facilities are more vitalized than those with the boundary wall of the residential building or the buffer zone. Second, the number of shops in street has positive influence on the vitality of a main street. Third, the vitality of a main street is effected by the entrance of apartment site.

• 한국전산유체공학회:학술대회논문집
• /
• 2001.10a
• /
• pp.138-143
• /
• 2001

An experimental model to enhance the mixing of parallel supersonic-subsonic jet ($M_1$=1.78 and $M_2$=0.30) is simulated with a numerical technique by modeling the wall-mounted cavity to a boundary condition of oscillating pressure. The computed pilot pressure distributions along three representative cross sections show a good agreement with the equivalent experimental data. The irradiation of acoustic wave in the ultrasonic range causes the mixing augmentation of jet and wake due to the transfer of vibration energy between fluid particles.

• Proceedings of the Korean Institute of Interior Design Conference
• /
• 2004.05a
• /
• pp.171-175
• /
• 2004

This study aims at the examination of the characteristics of sectional design by Raumplan through the analysis of his 12 houses in which his architectural design concept is clearly showed. The analysis proceeded through 12 sectional drawings, because of Raumplan is originated from the spatial concept which is dividing spaces with various differences of horizontal level. Through this investigation, three characteristics of sectional design by Raumplan which is to present : 1) Free horizontal variation by different level 2) Spatial division by splitted wall 3) Horizontal & vertical refraction of viewpoint & movement These characteristic seems like to including his intention to put into the various human behaviour in residence, it can be spatial clue to solve existential experience of 'homelessness' which is one of the biggest problems of modern times.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.5
• /
• pp.1301-1309
• /
• 1994

A study of heat transfer and thermophoretic particle deposition has been carried out for the Modified Chemical Vapor Deposition(MCVD) process. A new concept utilizing two torches is suggested to simulate the heating effects from repeated traversing torches. Calculation results for the wall temperatures and deposition efficiency are in good agreement with experimental data. The effects of variable properties are included and heat flux boundary condition is used to simulate the moving torch heating. A conjugate heat transfer which includes heat conduction through solid layer and heat teansfer in a gas in a tube is analyzed. Of particular interests are the effects of torch speeds and solid layer thicknesses on the deposition efficiency, rate and the tapered entry length.